Looking to replace the distributor in my 474. The GM HEI that's in it is pretty worn and like to find out what others like. I was considering the MSD with the 6AL box or maybe the ready to run unit. Some have said problems with these units including corrosion. How about the Mallory or DUI units. Appreciate your comments.

+1 on the DUI HEI - That's what I'm running in the Beast. It says something that when you order one from them, you have to give them lots of specific information about your engine, vehicle weight, drive train, etc. --- they take this information and use it to build a unit with an advance curve that's going to be right for YOUR car. Quality stuff.

I ran a DUI HEI unit in my SBC short-track car and was flawless. Currently have a stock HEI in my pontiac that I "recurved" myself with lighter weights, springs, and adjustments on the vacuum advance. Since I have a manual trans, I have my total mechanical advance of 36 deg coming in by 2,500 rpm or so, and maxing out around 48 deg with total mechanical & vacuum advance.

If increasing mechanical advance, be sure to check total advance at high vacuum becuase some vacuum advance units will crank it up to pretty high levels. I use a hand held vacuum pump connected to the HEI to easily check total advance while using one hand to hold rpms up, and the other hand running the timing light!

I assume if you order a custom unit from DUI, it should be pretty close, allowing you to set initial timing at idle and go!